1st time configuring a 1700 router. Need help changing IP address

ciscomoron · ‎10-10-2007

Hello, Newbie here!

I have an existing router that I need to change is IP address. We are making the change because we are switching ISP.

Here's what was given to my by ATT:

Internet Protocol (IP) Information:

ATT Serial: 67.x.x.25/30(255.255.255.252)

Customer Serial: 67.x.x.26/30(255.255.255.252)

LAN IP Block: 72.x.x.192/28(255.255.255.240)

On my 1700, it shows the following interface: Where should the above information go?

interface FastEthernet0

interface Serial0

Thank you in advance for your help.

Jon Marshall · ‎10-10-2007

Hi

From what you have said i would suggest it needs to go on your serial interface - this is the interface that connects to your ISP yes ?

If so

router(config)# int s0

router(config-f)# ip address 67.132.143.26 255.255.255.252

You will probably need to change your default-route on the 1700 as well to point to the ISP address.

HTH

Jon

Richard Burts · ‎10-10-2007

I certainly agree with Jon that 67.132.143.26 goes on your serial interface. I think that perhaps we need to know a bit more about how the router is currently configured before we say what to do with the default route. If the default route is configured like ip route 0.0.0.0 0.0.0.0 a.b.c.d then I agree that you will need to change a.b.c.d to 67.132.143.25. But if the default route is configured like ip route 0.0.0.0 0.0.0.0 serial 0 then there is no need to change it.

We also need to know a bit more about how the router is configured to know what to do with the LAN IP block that they gave you. If the router is configured to do address translation using a block of addresses from the previous ISP (and I would guess that it is) then you will need to change the address pool to use the LAN IP block. Or your router might have the public addresses configured on the FastEthernet interface, in which case the LAN IP block goes on the FastEthernet interface.

I would also suggest that you check to see if there are access lists which reference addresses from the previous ISP and if there are then these access lists need to be updated.

HTH

Rick

HTH

Rick

ciscomoron · ‎10-12-2007

Thanks for everyone's help.

And thanks for example on entering the command. The default route was already pointing to serial.